1. Field of the Invention
The present invention relates to the bonding of integrated circuit chips onto a continuous tape and more particularly to such an arrangement of bonding onto a tape on which are etched circuit conductor patterns as utilized in tape automated bonding systems.
2. Background Art
The process of bonding integrated circuit chips to a continuous tape on which are located etched circuit conductor patterns is known as tape automated bonding, or TAB. This particular process is desirable for three main reasons. The first of these is that the bonding area required on the integrated circuit is less than what is required for wire bonding. Secondly, the process is designed for automated handling, and finally, with the dice mounted on a tape the devices may be pretested before final assembly.
Such tapes are typically constructed by etching a conductive material which is supported by a flexible backing so that a series of conductors are formed. These conductors may then be aligned with bonding sites on the integrated circuit. After the conductors are etched, the support backing is etched away from the bonding region, thus creating a pattern of free beams. The support medium may be prepunched to form a bonding window. Once the beams are formed they are then plated with tin. Prior to the bonding cycle, the integrated circuit dice are bump plated with gold. The gold is used so that during the bonding cycle it may be dissolved with tin, which is plated on the tape, to form a gold/tin eutectic bond. This eutectic then forms the bond between the tape and the integrated circuit.
It is therefore both desirable and necessary to design a unique beam pattern for each and every integrated circuit which is to be bonded. This particular design limitation limits the use of the tape automated process to integrated circuits which will be assembled in high volume, since the cost of tape design and fabrication is also quite high.